Identification of the UDP-glucosyltransferase gene UGTA1, responsible for the first glucosylation step in the sophorolipid biosynthetic pathway of Candida bombicola ATCC 22214

Candida bombicola ATCC 22214 is applied commercially for the production of sophorolipids from renewable resources such as vegetable oils or waste streams. Although much research has been performed on optimization of fermentation conditions and on the influence of feed source and process parameters on sophorolipid structures and yields, the metabolic pathway of these important bioproducts remains unclear. Here, we identify a glucosyltransferase gene UGTA1 and show that the gene product is responsible for the first glucosylation step in the biosynthetic pathway of sophorolipids. Moreover, we provide evidence that the second glucosylation step is catalysed by a different glucosyltransferase that acts independently from the first. Therefore, the biosynthesis of sophorolipids by C. bombicola involves two glucosyltransferases that act in a stepwise manner. The UGTA1 gene described here is the first identified gene with a clear function in sophorolipid production by this economically important yeast.